A circuit is known for selectively providing electric supply voltage from an input feed line with a neutral conductor and a phase conductor to individual or parallel-connected groups of connected terminals each comprising a phase core and a neutral core, to which electrical units using electricity, for instance light fittings, are or can be connected. A known circuit comprises a neutral connection between the neutral conductor and each neutral core and a phase connection between the phase conductor and each phase core. It is further known to include in each phase core a switch, using which the relevant electrical unit or group of electrical units can be switched on and off. An end group of a switching and distribution device having electrical units connected thereto is herein protected by an overcurrent protection element which is accommodated in a switching and distribution device, wherein the cross-sectional surface of the phase cores and the neutral cores to the electrical units is adapted to the associated overcurrent protection element. This means in practice that, in the case where a plurality of electrical units are connected to an end group, the cross-sectional surface o the phase cores to the electrical units are therefore considerably overdimensioned.
An example; a number of lamps with a power of 100 W at 230 V_is connected to an end group of a switching and distribution device, wherein the cross-sectional surface of the phase cores and the neutral cores of the installation of the relevant end group is adapted to the overcurrent protection element of the end group in the switching and distribution device, wherein the maximum permissible current amounts for instance to 16 A. By way of comparison it is noted chat the current of each of said 100 W lamps amounts to less than 0.5 A.
In respect of the above described circuit system there are switching systems which are microprocessor- controlled and which find application in various types of building.
The first group of known systems are designed in accordance with decentralization principles and comprise a collection of decentralized control, feed and switching modules which are arranged above lowered ceilings and to which electrical units, for instance light fittings, can be individually connected. These modules are mutually coupled by means of a collection of data-bus lines which are in turn connected to a centrally deployed central control unit or CPU (Central Processor Unit). Operation of the lighting herein takes place either locally by means of signal media or centrally by means of control panels or a personal computer on the basis of a computer program.
A second group of known systems is likewise designed in accordance with decentralization principles wherein control and feed modules are placed above lowered ceilings and the switching device is incorporated in an electrical unit, for instance a light fitting. Coupling and operation take place in accordance with the description as given above for the first group of known systems.
A third group of known systems is designed in accordance with decentralization principles wherein the control modules are incorporated in the switching units and the feed and switching modules are arranged above lowered ceilings. Coupling and operation take place as stated in the description for the first group of known systems.
The described systems have for their object to simplify the installation of the systems by saving on the amount of cabling.
A fourth and final group of systems is designed in accordance with centralized principles. These systems are little used however, since heretofore the design of the distribution structure has not been sufficiently tested. Systems according to such a principle, in as far as they already exist, are therefore still much too expensive at the moment.
The first three stated, known decentralized systems have the Following drawbacks:
(1) An architect is a person who designs a building and therein makes use in many cases of lowered ceilings. These ceilings can be removable or non-removable. The architect is in practice always the one who makes the decisions in respect of the type of lowered ceiling which must be placed in a building. The technical aspect plays a subordinate role here. Two types of lowered ceiling are used, i.e. so-called removable and non-removable ceilings. In the case of removable ceilings the problem occurs that, if a problem arises with the decentralized equipment above the ceiling, these ceilings must officially be removed by a building contractor, since this falls within his responsibility. In the case of non-removable ceilings (for instance plastered ceilings), the problem arises that, when a problem occurs with the decentralized equipment above such a ceiling, this means demolishing thereof, which may be disproportionally costly. For the solving of a problem with the electrical installation the user of these installations is thus wholly dependent in these cases on the building contractor, which is an extremely unusual and very undesirable situation. In the best case it could be said that the service access to the installation merits special interest.
(2) Integration of control switching modules into components such as light fittings and switching units has the drawback of dependence on the manufacture. If a choice is made for a particular switching system, the use of fittings and switching units from the same manufacturer is also obligatory. This conflicts with the aspiration to have the greatest possible freedom in respect of choice of manufacturer of the components for installing, irrespective of the manufacturer of the switching system to be chosen.
(3) Decentralized installations become unfathomable after a period of time because over the years feed and switching components may gradually be added fairly randomly, and in practice this is never kept up to date in diagrams and modification data.
There is the further drawback that the operation of such systems or the manner in which the various parts are coupled and interconnected is not clear to the user of the installation. This has its origin inter alia in the typical knowledge level of the user in respect of such often xe2x80x9cintelligentxe2x80x9d components. The problem of serviceability also arises here once again.
(4) Decentralized control, feed and switching modules can often only be connected with much effort, for instance bus cable in, bus cable out, feeder cable in, switched lines out, control lines of signal media in. Such modules are also placed above ceilings in large quantities, wherein said operations must take place for each module individually. A large number of junctions thus result, the laborious nature of the connection thereof usually being underestimated.
(5) PLC (Programmable Logic Control) or microprocessor-controlled, intelligent control components are susceptible to obsolescence, similarly to computers, while installations are written off over a longer period, for instance in the order of 15 years. This means that a user of an installation must have the option of adapting the control engineering every few years to new technologies while maintaining the basic installation. With locally placed, intelligent components the complete installation must be modified, and this is expensive.
The conclusion which must be drawn from the above stated five drawbacks is that control, feed and switching equipment must at all times be placed at a location where it is easily and freely accessible to enable service provision in simple manner, for instance in one or more technical areas and certainly not above lowered ceilings, let alone in fixed ceilings. Switching devices and control device must also be made disconnectable to enable easy replacement of the control devices at a desired moment, wherein a simple centralized feed, switching and control wiring circuit must be developed to make the installation design easily controllable. The design of the entire installation must necessarily be recorded herein for the management thereof.
It is an object of the invention to substantially improve the intrinsic safety of the above described known circuit and to provide the option of installing the circuit at considerably reduced cost.
It is a second object of the invention to modify the known circuit such that it can be adapted in very flexible manner, making use of modular units, to individual requirements determined by the circumstances, with the possibility of easy adaptation of a circuit, once installed, to new requirements.
It is a third object of the invention to design the circuit such that it is easily controllable, wherein switching control components are easy to exchange, replace and monitor, wherein the effective useful life of the static components, among which can be included the wiring and cabling components, can be considerably increased.
A fourth and final object of the invention is to a body a switching system such that full synergy can result between optionally used data control systems, switch engineering, safety technology and energy distribution for electrical units.
In respect of the above stated objectives the invention generally provides a circuit for selectively providing electric supply voltage from an input feed line with a neutral conductor, a phase conductor and optionally an earth conductor to individual or parallel connected groups of connected terminals each comprising a phase core, a neutral core and optionally an earth core, to which electrical units using electricity, for instance light fittings, are or can be connected, which circuit comprises:
a neutral connection between the neutral conductor and each neutral core;
optionally an earth connection between each earth conductor and each earth core;
a phase connection between the phase conductor and each phase core, in which phase connection is arranged a current control element; and
an overcurrent safety element, for instance a fuse, which is incorporated in each phase connection and which limits the current to the maximum value determined for the relevant phase connection.
It is noted that optionally at least one earth conductor can be added to the circuit.
An example of such a circuit is embodied such that the current control element is a switch or relay.
Another embodiment has the special feature that a current control element is a controller, for instance a thyristor controller.
A very interesting possibility from a cost viewpoint consists of each phase core having a cross-sectional surface adapted to a maximum current through this phase core. This variant has the advantage that cores having considerably reduced cross-sectional surfaces can generally suffice, which provides a great advantage in terms of installation technique, since thinner cores are easier to handle and the possibility is moreover created of reducing the total dimensions of a bundle consisting of diverse cores, whereby more cores can be placed through an installation tube.
In similar manner the invention provides a variant wherein each neutral core has a cross-sectional surface adapted to the maximum current through this neutral core.
Specific advantages are achieved with an embodiment wherein each overcurrent safety element is arranged in the relevant phase connection close to the phase conductor. In this embodiment the advantage is gained that in any unsafe situation, in particular short-circuit, in one or more of the phase cores beyond an overcurrent safety element, a known safe situation is initiated immediately after activating of this overcurrent safety element. When switches are used as current control elements, switch contacts of lighter type can generally also suffice, since the switches no longer have to be adapted to the relatively large maximum current of the known Systems which is allowed in principle, but can be limited to those values, which are compatible with the limited maximum current determined by the relevant overcurrent safety element.
A specific embodiment has the special feature that only the part between the overcurrent safety element and the relevant terminal has a cross-sectional surface adapted to said maximum current through the relevant phase core.
Particular advantages are achieved with an embodiment, wherein the circuit is provided with a central control unit, for instance a switch panel, a PLC, a PC or the like, which is adapted to control the current control elements, for instance under program control with operation on the basis of external instructions, for instance co wands from a keyboard, a mouse, light sensors, warning sensors or the like, for instance according to the program present in the central control unit. Such an embodiment enables a great flexibility in combination with exceptionally great ease of operation.
The latter embodiment preferably comprises a circuit as according to claim 1, comprising a housing in which are accommodated a number of current control elements controllable by the central control unit via respective control terminals, and respective overcurrent safety elements connected in series to said elements, wherein
the phase, neutral and optional earth connections are jointly connected to respective poles of a first connector and the neutral connection is connected to a second pole of this first connecting means, which first connecting means is connectable to the input reed line;
a number of chase cores, a neutral core and optionally an earth core are connected to respective poles of a second connecting means, for instance a connector or terminal strip, which second connecting means is connectable to the terminals for the electrical units; and
a number of control terminals are connected to respective poles of a third connecting means, for instance a connector or terminal strip, which third connecting means is connectable to the central control unit.
A specific embodiment has the special feature that the second and/or the third connector is coupled fixedly to the housing.
The circuit according to the invention as described above can advantageously be further provided with bypass means for controlling the current control elements without the operation of the central control unit. The system can hereby be controlled in simple manner via the bypass provisions in an emergency situation.
A circuit with a central control unit can advantageously be provided with presentation means, for instance a monitor, with which diverse characteristic figures can be presented, for instance the total power or the total power per group of switched-on electrical units, the number of hours for which an electrical unit has been switched on, the energy consumption over a determined period and the like.
The invention also relates to a module comprising a housing in which are arranged a number of current control elements controllable by the central control unit via respective control terminals and respective overcurrent safety elements connected in series to said elements.
The invention further relates to an electrical cable, which is adapted to form part of a circuit according to the invention, wherein each phase core and each neutral core have a cross-sectional surface adapted to the maximum current through the relevant core. This electrical cable according to the invention comprises:
a number of insulated cores serving as phase cores and each having a relatively small cross-sectional surface;
an insulated core serving as neutral core with a relatively large cross-sectional surface;
optionally an insulated core serving as earth core with a relatively large cross-sectional surface; and
a jacket connecting and enclosing all said cores.